docs: def get_filter_by_name(filtername, **options):
      """Return an instantiated filter.
  
      Options are passed to the filter initializer if wanted.
      Raise a ClassNotFound if not found.
      """
      cls = find_filter_class(filtername)
      if cls:
          return cls(**options)
      else:
          raise ClassNotFound('filter %r not found' % filtername)